Soil Testing

What is Soil Testing?

The physical properties of the soil surrounding a KISSS line, largely determine how uniformly water can be distributed within an irrigated area. Understanding the soil is therefore critical to good design. In response to this, IWT has developed a laboratory test to predict how the KISSS system will perform based on the wetting behaviour of a representative sample of soil.


Why conduct a Soil test?

Soil testing takes the guess work out of deciding on the best spacing and depth for KISSS Subsurface Textile Irrigation lines.

Research and practical experience shows that the width of a wetting pattern can vary enormously with soil type. As a general rule, the wetting pattern is wider in heavy textured soils (high clay content) than in light textured soils (high sand content). However, soil texture is not a reliable guide to line spacing.

One reason for this is that some soils can become water repellent as they dry out. These hydrophobic or water repellent soils will severely limit the effectiveness of the irrigation system if they are not managed properly. 


When should a Soil Test be done?

Soil tests are highly recommended for any commercial or large scale KISSS installation. In these projects, good design can deliver both cost and water savings.

On small residential jobs, a soil test may not be warranted. In these projects, a conservative depth and spacing should be used. General advice on line spacing and depth for broad classes of soil is available here: kisss_installation_guidelines.pdf. If you are unsure about the soil type in your area, contact your local landscape or garden centre.



How can a Soil Test help?

Soil testing will allow you to:

  • Determine the appropriate installation spacing and depth that will give a uniform wetting pattern.
  • Identify nonperforming and problem soils. Some soils are unsuitable for subsurface irrigation. The most common problems are water repellency, high porosity (usually soils made with compost) and sodicity (soils lose structure when wet, slowing capillary absorption and restricting oxygen supply to roots). Problem soils can sometimes be ameliorated or replaced.
  • Check out soils from you local landscape supplier for suitability in a KISSS installation. If you are buying top soil for a project it makes good sense to first check that it is compatible with subsurface irrigation.
  • Investigate the benefit of amending problem soils to improve capillary wetting. Sand, lime, dolomite, gypsum, coir and wetting agents can be used for this purpose.
  • Estimate the volume of water stored in the root zone after an irrigation. This information is helpful when developing an irrigation schedule.
  • Determine the capillary absorption rate of the soil.  This information can be used to choose the KISSS product with the best flow rate for the soil.


How to get a Soil Test

Irrigation & Water Technologies offer a soil test that has been developed specifically for Subsurface Textile Irrigation. This is not available through any other laboratory.

To arrange testing of a soil for your project,email


Collecting a soil sample for testing

The sample must be representative of the soil that will overlay the irrigation system. Mix soil from several areas to avoid sending something that is atypical of the site. More than one sample may be required if the soil texture varies greatly across the site.